In recent years, a copying apparatus in which a toner cartridge is mounted on a developing device and a toner is replenished from the toner cartridge has been put to practical use.
A copying apparatus of this type has a removable toner cartridge. The cartridge is exchanged when the toner in the cartridge runs out.
Generally, in the copying apparatus of this type, it is preferable to use a toner cartridge the manufacturer guarantees in accordance with the structure and standards of the machine frame.
In most conventional copying apparatuses, however, the toner density in the developing device is checked, and toner replenishment from the cartridge is controlled. When the toner density does not reach a predetermined value even after toner replenishment has been performed for a predetermined period of time, it is instructed that the user exchange the cartridge.
Since it is the user who exchanges the toner cartridge, a standard cartridge guaranteed by the manufacturer is not always used.
Even when a non-guaranteed toner cartridge (other than the standard product) is used, a certain degree of copying performance is ensured. In this case, however, the performance of the copying apparatus is not fully attained, and a trouble may be caused.
In the field of the copying apparatus, a technique of detecting whether or not a developing device has been installed in the full-color copying machine has already been proposed, as is disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2-93480.
Also, Jpn. Pat. Appln. KOKAI Publication No. 63-193156, for example, discloses an image forming apparatus, in which a specific binary pattern identification number marked at one end of a unit integrally comprising a photosensitive drum and a developing device is read when the unit is mounted in the main body, so that a mounting error of the unit can be recognized.
However, the arrangement for identifying the developing devices according to these proposals can be easily imitated. A strong demand has arisen for an appropriate countermeasure for a toner cartridge that can be imitated more easily than the developing device.